Conventionally, refrigeration apparatuses have included air-conditioning apparatuses used to cool and heat room interiors of buildings or the like by performing a vapor-compression refrigeration cycle.
In this type of refrigeration apparatus, when the temperature of the refrigerator oil is low while the refrigeration apparatus has stopped and the pressure of refrigerant in the compressor is under a certain condition, the amount of refrigerant dissolved in the refrigerator oil in the compressor increases. When there is an overlap of conditions such as the refrigeration apparatus being out of operation for a long period of time and/or a change in the refrigerant temperature (or the outdoor temperature), it causes a phenomenon known as stagnation, and a large amount of refrigerant dissolves in the refrigerator oil inside the compressor. When the refrigerant stagnates in the refrigerator oil and the concentration of the refrigerator oil decreases, there is a risk that the viscosity of the refrigerator oil will decrease and the compressor will not be sufficiently lubricated.
In conventional practice, to prevent refrigerant stagnation in the compressor, a countermeasure has been employed in which a heater is attached to the outer periphery of the compressor, and the refrigerator oil inside the compressor is heated while the refrigeration apparatus has stopped to ensure that the refrigerant does not stagnate. There are also cases in which the refrigerator oil inside the compressor is heated by open-phase current conduction to the motor.
However, when current is conducted to the heater in order to heat the refrigerator oil inside the compressor while the refrigeration apparatus has stopped, a certain amount of power is consumed as standby power, and the amount of power consumed by the refrigeration apparatus is increased.